mid-14c., "the science of religion, study of God and his relationship to humanity," from Old French theologie "philosophical study of Christian doctrine; Scripture" (14c.), from Latin theologia, from Greek theologia "an account of the gods," from theologos "one discoursing on the gods," from theos "god" (see theo-) + -logos "treating of" (see -logy). Meaning "a particular system of theology" is from 1660s.